Auckland Zoo's carnivore team leader, Bruce Murdock, said the zoo was "absolutely stoked" with the birth.
"This birth is a fantastic result, especially as Bo was only introduced to Sagar last August, and given female red pandas come into season just twice a year and a male has only a one to two-day window to mate a female," Mr Murdock said.
"We couldn't ask for a better mum in Bo. She's doing an exceptional job, staying in the nest box for long periods and feeding her cub up to six times a day, and being very attentive."
Mr Murdock said red pandas develop slowly and are dependent for at least three months, so it could be another eight to 10 weeks before visitors to the zoo see the cub venturing out of its nest box and around the enclosure with mother Bo.
"We're keeping a regular watch on this cub, but taking a very hands-off approach so Bo can continue to do the great job she's doing, and we minimise any potential stress for her. Around late February will be a safe time for us to do a full vet check on the cub. We're not absolutely sure, but bets are on that we have a female," Mr Murdoch said.
As part of an international breeding programme for the threatened species, Auckland Zoo sent female red panda Khosuva to India's Darjeeling Zoo in 2010, where she has been paired up with a breeding male as part of Project Red Panda.
The plan is for Khosuva's offspring to be released into the wild in Nepal.
In return, Sagar arrived at Auckland Zoo in 2010 from Darjeeling Zoo to breed.
Besides Bo, Sagar and the newborn, Auckland Zoo has two other red pandas - 16-year-old Maya and her 12-year-old daughter Amber.
